Right now, the only utility is a function for blending colors in
HSV space. This has the effect of "travelling around the color
wheel", which can be especially nice when one wants to blend
smoothly from one color to another (blending in RGB space can tend
to travel across some icky brown/grey colors).

Documentation

Blend two colors in HSV space---that is, linearly interpolate
between their hues, saturations, and values independently
(wrapping around appropriately in the case of hue). In
particular, hsvBlend a c1 c2 is like doing (a-1)*c1 + a*c2 in
HSV space. That is, a parameter of 0 results in only the first
color; 1 results in only the second color; and anything in
between results in a blend.